Berthold has learned from the mistake.
Motivated by Kona's sales, he went back to the drawing board and created a new suspension design. He calls it the "missing link," and says it is even better than the product he worked on for Kona, dubbed the "magic link."
But, it wasn't easy.
"I probably had 1,000 iterations of [designs] on my computer," Berthold tells CNBC Make It. "This is like against all odds determination."
While engineering is usually just about incrementally improving something, Berthold wanted to reimagine the way a bike suspension works. To do that, he decided to start from scratch.
"Designing, usually you're kind of relying on something else that has been done," he explains. But when inventing something new, "You want to forget, disavow, any knowledge of what anyone else has done."
In November 2015, he launched a Kickstarter for bikes built with the "missing link." That marked the beginning of his new company, Tantrum Cycles.
"This time I paid for the patent, I paid for the prototype," he says on the show, adding that he's sunk nearly $200,000 into the business. His bicycles sell for $7,000 at the high end, and $3,500 for a cheaper model.
"I decided I'd gone this far, I'm going to do it myself," he says.
It's part of Berthold's life's work. After serving in the Air Force for three years, Berthold graduated from the University of New Mexico in 1985 with a degree in mechanical engineering and went to work in professional car racing. He says he opted to pursue cars because at the time, there wasn't much complex engineering in bicycles.
"Bicycles were still the same as they had been forever, so I went into car racing," he says. But in the early 1990s, interest began to build around re-inventing the technology in bikes. That's when he started thinking about how to re-work suspensions.